Health, disease and the development of medicines
Communicable disease
health-a state of complete physical, mental and social well-being
Diseases can be grouped into two types:
communicable, which can be transferred from one person to another
non-communicable, which are not transferred between people
pathogen- an organism that causes a disease
lifecycle of a pathogen-They infect a host, reproduce themselves or, if a virus, replicate, spread from the host, and infect other organisms.
diseases can be transferred in many ways but some of the most common are:
Direct contact
water
air
Unhygienic food preparation
or a vector
virus lifecycle- virus replicates its DNA and protein coating
they then assemble themselves
this causes host cell to burst
the virus then infects nearby cells
Cholera is a bacterial infection often transmitted in dirty water or contaminated food
Chalara ash dieback- species of fungus that infects ash trees
how to prevent virus from spreading
Sterilising water
Suitable hygiene
Vaccination
Contraception
plant disease
Scientists want to identify potential plant pathogens as soon as possible in order to reduce the spread of an infection. The following steps may be taken in the process of identifying a disease:
Scientists will go to the site if there is a report of an infection.
To avoid any confusion, it is critical that they investigate other factors that may be causing similar symptoms. Leaf damage, for example, could be caused by a pathogen or grazing animals.
The scientists will look for any environmental factors, such as pollution, that may be affecting the plants.
Finally, they will photograph the symptoms and collect samples for testing in a laboratory.
plant defences
physical
Bark
thorns and hairs
drooping leaves
Treating, curing and preventing disease
defence against infection
The body is constantly defending against attacks from pathogens. The first line of defence against infection stops the pathogens from entering your body. These first lines are general defences, and are not specific to fight against certain types of pathogen. We call this non-specific, and they can be physical or chemical barriers.
physical defences
skin
nostril hairs
chemical
stomach acid
lysozymes
The immune system defends against disease
White blood cells are referred to as phagocytes. They are drawn to pathogens. They envelop them in blood, bind to them, and engulf them.
The phagocyte's membrane surrounds the pathogen, and enzymes found within the cell break it down in order to destroy it. Because phagocytes do this to all pathogens they encounter, we refer to them as 'non-specific.'
Lymphocytes are a type of white blood cell as well. They recognise antigens, which are proteins on the surface of pathogens. Lymphocytes produce antibodies when they detect that the proteins and pathogens are foreign and do not occur naturally in your body. This may take several days, during which you may feel ill. Pathogens stick together as a result of the antibodies produced by lymphocytes, making it easier for phagocytes to engulf them.
A memory lymphocyte is a type of lymphocyte that can 'remember' antigens from a previous pathogen infection.
Immunisations allow the introduction of an inactive form of the disease-causing pathogen into the body, which contains a specific antigen. The immune system, specifically white blood cells, responds by producing complementary antibodies that target and attach to the antigen.
making medicines
plant extracts
Certain drugs can be extracted from natural sources, and this has been known for a long time. The ancient Greeks, for example, used willow bark to treat fevers and pains. Salicylic acid was later discovered to be the active ingredient. Chemists modified this to create aspirin, which is less irritating to the stomach than salicylic acid. Another example is digitalis, a heart drug derived from foxgloves.
Plants are still important today, but most drugs are now developed in laboratories by pharmaceutical company scientists. These companies now have synthetic versions of plant extracts that they use as a starting point for developing new drugs.
The development and testing of new drugs
Before doctors can prescribe and patients can take new drugs, they must be tested and trialled. This allows the drug to be tested for
Safety This is important as some drugs are toxic, and have other side effects that might be harmful to people.
Effectiveness This is also known as efficacy, and checks how well the drug cures the disease, or improves symptoms.
Dosage This varies, and has to closely controlled, as too high a concentration might be toxic.
monoclonal antibodies
Monoclonal antibodies are identical copies of one type of antibody.
uses for monoclonal antibodies
pregnancy tests
cancer diagnosis and treatment
Cancer is a non-communicable disease. Explain how smoking can affect the development of cancer. Define risk factors in your answer. [4 marks]
Risk factors are things that increase a person's chances of developing a disease. They can be a person's lifestyle or substances in their body or environment.
Cigarette smoking is a risk factor for lung cancer.
Describe the differences between phagocytes and lymphocytes. [4 marks]
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